An “air handler” or “air handling system” is that portion of a central air conditioning system that moves the conditioned (cooled) air throughout a structure's ductwork or air flow enclosure. Air is forced by a fan through a cooling coil. If the fan is downstream of the cooling coil, the air handler is a “draw-through” type system. If the cooling coil is downstream of the fan, it is referred to as a “blow through” type air handler.
In a draw-through type system, some heat is added to the air by the fan after it is cooled. On the other hand, in the blow-through type system, the air is cooled downstream of the fan, so that the air entering the conditioned space is cooler. For this reason, blow-through air handling systems are preferred; because the air entering the space is cooler, less air is required to reach the desired room temperature. This, in turn, reduces the costs of the air handling system including the energy required to operate it efficiently.
Blow-through air handlers can be problematic in some applications, such as hospitals, pharmaceutical plants, and other facilities with “clean rooms,” where the conditioned air is passed through a final air filter downstream of the cooling coil and prior to entering the space. Water from the nearly saturated air leaving the cooling coil sometimes condenses on the filter, eventually causing it to become soaked with moisture. Because the air leaving the coil is nearly saturated and because the temperature of this air fluctuates over such a small range, condensate in the filter has no opportunity to evaporate.
Thus, there is a need for blow-through air handling system that reduces condensate on air filters downstream of the cooling coil. There is a need for a heat exchanger system that can be retro-fitted to pre-existing air handlers plagued with wet air filters. There is a need for a simple reheat solution that will add as little as one-half to one degree Fahrenheit (0.5-1° F.) to the air leaving the cooling coil and before it enters the filter; this small amount of additional heat would reduce or eliminate condensation in the filter. There is a need for a simple reheat solution that is inexpensive to buy, to install, and to operate. There is a need for a reheat solution that would require no source of heated water or special electrical circuit. There is a need for a reheat solution that would require little or no modification to the air handler cabinet. There is a need for a reheat solution with a relatively low capacity so that its size and cost are minimized. There is a need for an adjustable run-around heat recovery system that can be sized for use with different size cooling coils, eliminating the need for expensive, customized options.